The long-term objective of this research is to understand the process by which human epithelial cells recognize and adhere to one another. Alterations in these interactions have been documented in malignant cells and in abnormal development. We have shown that cell-cell adhesion is mediated by an integral membrane protein, cell-CAM 120/80. The goal is to isolate, produce antibodies and to characterize the proteins specifically associated with cell-CAM 120/80 that may be important to the regulation of adhesion. The possible roles of these proteins include: 1) a specific protease which cleaves gp120 to gp80; 2) a receptor for gp120; and 3) a membrane-cytoskeletal connection. In addition, the work proposed here aims to continue the work begun on the molecular cloning of cell-CAM 120/80 and the proteins associated with it. To date, three possible clones have been isolated and characterization of them has begun. When clones are identified as specific for cell-CAM 120/80, they will be used in sequence analysis as well as analysis of the expression of this important cell adhesion molecule and analysis of the genes encoding it.